The present invention relates generally to methods and apparatus for automatically replacing fully wound yarn tubes on a textile ring spinning machine, ring twisting machine or like textile machine with empty yarn tubes and, more particularly, to a method and apparatus for monitoring the proper operation of an automatic bobbin changer for grasping and releasing yarn tubes in executing the exchange procedure.
Automatic bobbin changers are known which are operable to simultaneously grasp a plurality of yarn tubes at either or both the spindles of a textile ring spinning or twisting machine or the support pins of a tube supply arrangement and for subsequently releasing the grasped tubes to execute a simultaneous replacement of all spinning tubes in yarn winding operation on the textile machine with a corresponding number of empty yarn tubes. In executing this operation, a risk exists that the automatic bobbin changer may fail to properly grasp one or more of the yarn tubes to be grasped or may fail to properly release one or more of the yarn tubes previously grasped.
Specifically, if one or more fully wound yarn tubes (commonly referred to as bobbins) to be doffed from the spindles of a ring spinning or ring twisting machine are not grasped and removed from the spindles by the automatic bobbin changer, the tube or tubes remaining on the spindles will obstruct the bobbin changer from properly carrying out the subsequent placement of an empty tube or tubes on the affected spindles, necessarily resulting in damage to the tubes and perhaps also to the textile machine and the bobbin changer with an attendant undesirable down time in the normal operation of the machine.
West German Offenlegungschrift 2 226 077 discloses the provision of a light beam passing through the area of a textile machine occupied by fully wound tubes to be withdrawn for purposes of detecting an interruption in the light beam and generation cf a machine stoppage signal when a tube remains on a spindle of the machine after the withdrawal operation.
Likewise, if an automatic bobbin changer fails to properly release one or more tubes grasped by the changer, the non-released tube or tubes will obstruct and collide with another tube or tubes during subsequent attempted operation of the bobbin changer to grasp another tube or tubes, also causing damage to the tubes and possibly to the bobbin changer and the textile machine. If the bobbin changer fails to grasp an empty tube, the changer necessarily fails subsequently to place the missing empty tube onto a respective spindle of the textile machine whereby resumption of the machine operation causes yarn to be wound about the bare spindle, removal of which is difficult, time consuming and expensive to accomplish.